The invention relates to an apparatus for the insertion of weft threads in a weaving machine and to a method for the insertion of weft threads in a weaving machine as well as to a weaving machine with an apparatus of this kind and for carrying out a method of this kind.
In DE 32 00 638 A1 an air jet weaving machine is described which comprises a nozzle with a mixing tube for the insertion of weft threads and a reed for beating up the latter. A thread clamp is arranged in the mixing tube of the nozzle in order to firmly clamp the weft thread during the severing or during the standstill of the weaving machine and thereby to prevent a jumping back of the weft thread in the nozzle. This arrangement of the thread clamp permits arranging the mixing tube close to a weft thread guiding passage which is formed in the reed, so that during the insertion the deviation in the desired position of the weft thread between the mixing tube and the weft thread guiding passage can be kept small.
WO 02095105 A1 discloses, in FIGS. 5 and 6 of the specification, an apparatus for the insertion of weft threads in a weaving machine which contains a plurality of nozzles, each with a mixing tube. The nozzles are each provided with a clamping device 1A which are connected via lines 15 to control valves 17 in order to charge the clamping devices with compressed air or vacuum. The control valves 17 are activated by a control system 20.
In the conventional apparatuses for the insertion of weft threads the latter are held firmly in the individual nozzles after the insertion by means of a retaining air flow in normal operation in order to prevent a jumping back of the weft threads in the nozzles. In contrast, when the weaving machine is stopped, the weft threads are held firmly by clamping devices which are arranged in the mixing tube of the nozzles; and the retaining air flow is interrupted since there is the danger when the machine stands still for a longer period of time that the weft threads will be damaged by the retaining air flow. The clamping devices have the disadvantage however that they complicate the threading in of individual weft threads into the associated nozzles, since the clamping devices must be opened individually via the weaving machine control system for the threading in. The individual control of the clamping devices is connected with additional cost and complexity since in addition to one control valve per clamping device a supply line for the compressed air is also needed.